1. Field of the Invention
The present invention relates to a scanning probe microscope having a self detection type probe including a piezoresistance element.
2. Description of the Related Art
An atomic force microscope (AFM) serving as one of a scanning probe microscope (SPM) is used for various electrical property measurements such as a current measurement, a dielectric measurement, and a potential measurement by a Kelvin probe force microscope or the like other than the surface shape measurement of a sample. The AFM carries out various electrical property measurements by using a cantilever provided with a probe having a conductive property at its front end.
Upon this measurement, deflection (warpage) of the cantilever is measured in a system called an optical lever system and depending on this measurement result, a distance between the probe tip and the surface of a sample is always controlled constant.
This optical lever is a system that measures the deflection of the cantilever by irradiating a laser light toward a reflection face formed on the rear surface of the cantilever from a light source and detecting the laser light reflected on the reflection face by a photo detector that is divided into two or four. In other words, if the cantilever is detected in compliance with irregularities of the surface of the sample, a reflection position of the laser light is different depending on the deflection, so that the incoming position of the laser light to be inputted in the photo detector is different. Therefore, by detecting this incoming position of the laser light, the deflection of the cantilever can be measured.
In addition, by feedback-controlling a sample table having the sample mounted thereon in a direction perpendicular to the surface of the sample on the basis of the deflection of the cantilever detected in the optical lever, as described above, it is possible to scan the sample while always controlling the distance between the probe tip and the surface of the sample constant.
In addition, in this case, by scanning the sample and applying a predetermined voltage and current to the cantilever, it is possible to carry out electric measurement of the sample. [Patent document 1] JP-A-2004-294218 [Non-patent document 1] By Alexander Olbrich et al., Applied Physics Letters, volume 73, number 21 (US), “Conducting atomic force microscopy for nanoscale electrical characterization of thin SiO2”, 23 Nov. 1998, P. 3114-3116 [Non-patent document 2] By Yasuo Cho et al., Applied Physics Letters, volume 75, number 18 (US), “Scanning nonlinear dielectric microscopy with nanometer resolution”, 1 Nov. 1999, P. 2833-2835 [Non-patent document 3] By Joseph J. Kopanski et al., Materials Science and Engineering B44, “Scanning capacitance microscopy applied to two-dimensional dopant profiling of semiconductors”, 1997, P. 46-51 [Non-patent document 4] By R. Shikler et al., Applied Physics Letter, volume 74, number 20 (US), “Potential imaging of operating light-emitting devices using Kelvin force microscopy”, 17 May 1999, P. 2972-2974.
However, the measurement method of the electric property by the above-described conventional optical lever system involves the following problems.
In other words, there is a disadvantage that the laser light is partially irradiated on the surface of the sample that is a target of the measurement as leaked laser light, hereinafter referred to as light leak, upon irradiation of the laser light from the light source to the cantilever in the optical lever system. Accordingly, the measured electrical property turns out to be a property of the sample on which the light leak in the optical lever system is irradiated. In other words, the light of the sample is excited by the light leak leading to a noise, so that the true electrical property of the sample cannot be measured.